Known tape printing apparatus are disclosed in U.S. Pat. Nos. 4,927,278, 4,966,476 and 4,815,871. The printers each include a printing device having a cassette receiving bay for receiving a cassette or tape holding case. In U.S. Pat. No. 4,815,871, the tape holding case houses an ink ribbon, a transparent image receiving tape and a double-sided adhesive tape. The adhesive tape is secured at one of its adhesive coated sides to the image tape after printing and which has a backing paper peelable from its other adhesive side. With each apparatus, the image transfer medium (ink ribbon) and the image receiving tape (substrate) are in the same cassette.
A different type of tape printing apparatus is described, for example, in U.S. Pat. No. 5,458,423, the content of which is herein incorporated by reference. In this printing apparatus, the substrate tape is similar to that described in U.S. Pat. No. 4,815,871 but is housed in its own tape holding case while the ink ribbon is similarly housed in its own tape holding case.
In all of these devices, the image receiving tape passes in overlap with the ink ribbon to a print zone. The print zone consists of a fixed print head and a platen against which the print head can be pressed to cause an image to transfer from the ink ribbon to the image receiving tape. There are many ways of doing this, including dry lettering or dry film impression, but the most common way at present is thermal printing where the print head is heated and the heat causes ink from the ink ribbon to be transferred to the ink receiving tape. Alternatively, the print head may be in direct contact with a thermally sensitive image receiving tape whereby when the print head is heated, an image is defined on the image receiving tape.
U.S. Pat. No. 5,043,748 discloses an ink jet recording apparatus wherein the recording medium is transported by means of a DC motor. In order to avoid stoppage of the motor due to the lack of image data to be printed, which results in poor print quality, it is proposed to control the speed of the motor to depend on the speed of data transfer from a host computer.
A disadvantage of known tape printers is that they generally have a constant print speed, such that the printing process may stop due to lack of image data awaited from a connected host computer. Further, they require a relatively large and expensive power supply, which must be capable of providing the print head with power even when a full dot line is not printed.
Therefore, it is desirable to provide a label printing apparatus which overcomes the disadvantages of the state of the art. The present invention provides a label printing apparatus which meets these requirements.